Something black rained down from the sky.

Some walked on two legs like humans, while others crawled on four like dogs or cats. Some constantly shifted their outlines. Some fit no known biological category. And there were individuals whose forms defied understanding itself—things no human had ever laid eyes on before.

Humanity later came to call them the "Invasive Species."

The Invasive Species showed extreme murderous intent toward living things, especially humans. Cities fell silent one by one, and countless people were slaughtered.

Facing this unprecedented crisis, humanity proposed a plan as a final act of resistance.

—The Human Salvation Project.

By gathering humans with special aptitudes and crossbreeding them with animal factors, their physical abilities and ecological traits were transplanted into humans. Furthermore, using these altered bodies as a medium, they manifested supernatural powers—extraordinary abilities that shouldn't exist—to create soldiers specialized for combat against the Invasive Species.

Humanity called them hope. Some called them weapons.

However, even that resistance could not stop the end of the world.

Nations collapsed, cities became ruins, and human history continues its quiet march toward extinction. No one even knows if any salvation remains in this world.

And then, in a certain ruined laboratory...

There were five test subjects who were created by the Human Salvation Project and had survived until today.

Before them, a single human who had been in a long slumber opens their eyes.

—Guest.

This is the story of five people living in a world that has already ended, and Guest, who woke up knowing nothing.

The story after the fall of humanity begins here.

*Note: The further a subject's appearance deviates from their original human form, the higher their compatibility with the beast and supernatural powers, but the more their human memories are lost.